US3253169A - Synchronous motors - Google Patents

Synchronous motors Download PDF

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Publication number
US3253169A
US3253169A US259880A US25988063A US3253169A US 3253169 A US3253169 A US 3253169A US 259880 A US259880 A US 259880A US 25988063 A US25988063 A US 25988063A US 3253169 A US3253169 A US 3253169A
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United States
Prior art keywords
coil
magnetic
rotor
motor
stator
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Expired - Lifetime
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US259880A
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English (en)
Inventor
Arthur W Haydon
Charles S Daniels
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Consolidated Electronics Industries Corp
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Consolidated Electronics Industries Corp
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Priority to US259880A priority Critical patent/US3253169A/en
Priority to NL6401518A priority patent/NL6401518A/xx
Priority to BE644065D priority patent/BE644065A/xx
Priority to DE19641488127 priority patent/DE1488127A1/de
Application granted granted Critical
Publication of US3253169A publication Critical patent/US3253169A/en
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K1/00—Details of the magnetic circuit
    • H02K1/06—Details of the magnetic circuit characterised by the shape, form or construction
    • H02K1/12—Stationary parts of the magnetic circuit
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F13/00—Apparatus or processes for magnetising or demagnetising
    • H01F13/003—Methods and devices for magnetising permanent magnets

Definitions

  • the present invention relates to alternating-current synchronous motors and, more particularly, relates to improvements in self-starting, bidirectional synchronous motors of the type having but a single set of salient stator poles.
  • pole members themselves are equiangularly spaced around a cylindrical rotor member of ferrite material which is magnetized in localized regions so as to provide pairs of non-salient magentic poles uniformly spaced about the axis of rotation, with adjacent poles being of opposite magnetic polarity.
  • the rotor, the stator piece, and the encircling field coil are all contained within a housing of ferromagnetic material comprised of a cupshaped cover piece secured to a mounting plate.
  • the motors described in the aforesaid patent were a revolutionary change and reduction in number of essential parts over prior art motor designs which heretofore had required two or more sets of stator poles of instantaneously opposite magnetic polarity.
  • the motor embodiments described in this patent possess, without the use of shading poles, mechanical devices or the like, a reliable self-starting characteristic by reason of the fact that the rotor, upon de-energization of the motor, consistently assumed a predetermined quiescent (i.e., stopping) position relative to the stator pole members which produced maximum starting torque when the motor was again energized.
  • the novel motors described in the aforesaid Everard et al. patent represent a marked advance in the art.
  • certain disadvantages have been experienced with some of the motor embodiments described in the patent because of the rather sizeable air gaps present between the stator poles, the rotors, and the cover plate.
  • the existence of a low reluctance magnetic circuit path provided outside the field coil by the ferromagnetic motor housing diverts a substantial portion of the stator flux and prevents it from coupling with the rotor poles, thus resulting in substantial power dissipation and a concomitant decrease in motor efficiency.
  • the location of the stator pole members inside the field coil requires, by necessity, that the diameter of the rotor member, which determines the torque-moment of the motor, must be substantially less than the diameter of the field coil which encircles it. Accordingly, only a fraction (typically /2 or less) of the dimension of the motor in the direction transverse to its rotational axis is utilized as a moment arm for generating torque in these motors.
  • the present invention is directed to AC. self-starting synchronous motors, of the type having but a single set of stator poles, which have significantly improved performance characteristics and other important advantages "ice over the motor embodiments exemplified in the aforesaid Everard et al. Patent 3,059,131.
  • motor embodiments of the present invention have substantially improved efliciency, power, and torque characteristics.
  • motor embodiments of the present invention can operate at up to four times the etiiciency, and generate up to four times the running torque, of the former.
  • the motor housing has no functional role in the magnetic circuit of the motors of the present invention, fewer and less costly parts are required in the construction as the cover piece of the housing may, if desired, be eliminated, and the mounting plate need not be made of ferromagnetic material.
  • the significant improvement in performance characteristics of motors of the present invention are obtained primarily because ('1) substantially all the magnetic flux generated by the field coil is tightly confined, with very low leakage, to a single, low reluctance magnetic circuit path passing through the rotor and outside the field coil, and (2) the improved lightweight rotor design has a diameter approximately twice that of the prior art Everard et al. motors and utilizes only a small amount of magnetizable material in the form of a thin annular ring around the periphery of the rotor.
  • the magnetizable ring portion of the rotor in a preferred embodiment, comprises a flexible strip of rubber or plastic-bonded anisotropic barium ferrite material.
  • the motor embodiments of the present invention produce good starting torque and retain the reliable self-starting action of the motor devices described in the Everard et al. patent, as the rotor element of these motors will consistently assume a quiescent position which bridges the space midway between adjacent stator pole members.
  • FIG. 1 is an exploded, perspective View of one motor embodiment of the present invention.
  • FIG. 2 is an exploded, perspective View of an alternative motor embodiment of the present invention.
  • FIG. 3 is a cross-sectional view of the assembled motor embodiment of FIG. 1.
  • FIG. 4 is a cross-sectional view of the assembled motor embodiment of FIG. 2.
  • FIG. 5 is a perspective view of a jig means suitable for magnetizing the pole regions on the rotor element of the motor embodiments of the present invention.
  • FIGS. 1 and 3 of the drawings One embodiment of the invention is shown in FIGS. 1 and 3 of the drawings.
  • the major elements of the motor comprise a mounting plate 12, a stator polar structure 14, a field coil 18, a cup member 22, and a permanent-magnet rotor 21formed of a supporting wafer element 27 and a peripheral ring 30 of magnetizable material.
  • the mounting plate 12 is of conventional form and may be composed of any suitable material of requisite strength, such as aluminum or steel, for example.
  • the stator member 14 is of ferromagnetic material, such as iron, and comprises a circular base from which projects a set of, exemplarily, twelve salient members or poles 13.
  • Thes pole members 13 are arranged on a substantially cylindrical surface at uniform, angularly-spaced positions about the periphery of the stator piece 14. Both the base of the stator member 14 and the mounting plate 12 have center apertures therein adapted to receive and engage an end of a core piece which contains a bearing assembly 17 for supporting the rotor 21.
  • a field coil 18 of conventional design wound on a circular bobbin form for providing energizing flux for the motor.
  • a cup-like member 22 of ferromagnetic material Placed against the other end of the field coil 18 is a cup-like member 22 of ferromagnetic material which has a central opening adapted to secure the other end of the core 20 of the bearing assembly 17.
  • the cup member 22 has a peripheral flange portion 22a which extends outside of and around the field coil 18 for a portion of the axial length of the latter.
  • the cup member 22 has a lesser diameter than the stator piece 14, and accordingly, the flange 22a is overlapped by the salient pole members 13 of the stator piece, thus forming an annular air gap therebetween.
  • the permanent-magnet rotor element 21 Mounted above the cup-member 22 and secured to the shaft 29, which is supported for rotation in the core of the bearing assembly 17 (which, e.g., may conventionally include a pair of sintered bronze bearings and a lubricating wick 16 carried inside) is the permanent-magnet rotor element 21. If desired, a pair of thrust washers 25 may be interposed between the rotor 21 and the face of the bearing assembly 17.
  • the rotor is of circular configuration and comprises a peripheral ring member secured by a suitable binder, such as cement or epoxy resin, to the turned lip portion 28 of a thin, supporting rotor framepiece 27 which'is securely attached to the shaft 29 by means of hub piece 26.
  • the rotor framepiece element 27 is made of a ferrous material which serves to capture any stray leakage flux and direct it to the annular air gap formed between the flange 22a and the salient pole members 13.
  • the framepiece can be considered magnetically as being part of the cup member 22.
  • the magnetizable ring 30 is preferably composed of a flexible strip of plastic or rubber-bonded anisotropic ferrite material having a plurality of permanently magnetized regions 31 of alternate polarity induced therein.
  • One material found especially suitable in certain motor embodiments of the present invention is a rubber-bonded barium ferrite material having exceptionally good magnetic properties, including a high coercive force of approximately 1,300 oersteds and a maximum energy product of approximately .9 10 gauss, as well as flexibility, machinability and other goo-d mechanical qualities, and is commercially available, for example, under the name Plastiforrn from Leyman Corporation of Cincinnati, Ohio.
  • This ferrite rotor material 'being magnetically hard, enables the placing of poles of opposite polarity very close to each other on the periphery of the rotor to form a non-salient pole type rotor.
  • the magnetic field intensity established by these poles does not deteriorate appreciably during operation or with age once the rotor is subjected to the alternating flux field of the stator at the lowest temperature at which it is anticipated the motor will be run.
  • FIG. 5 One practical manner for inducing the magneticallyoriented regions 31 which constitute the poles of the rotor 21 is illustrated in FIG. 5.
  • the assembled rotor 21, of the motor embodiment of FIGS. 1 and 3, for example, is placed within a drum-like magnetizing fixture, generally indicated at 38, consisting of a top ring 40 and a bottom ring 41, both of which are formed of insulating material and suitably supported in coaxial spaced relation as shown.
  • Heavy conductive wire 42 is looped about the top and bottom rings a suflicient number of times so that there are as many individual spans 43 of wire between the rings as there are poles to be formed in the periphery of the rotor.
  • the loops of wire should be formed so that each span 43 of wire between the rings 40 and 41 is substantially parallel to the axis of the fixture 38 and all the spans are at equally spaced locations about the rings.
  • the leads 44 are provided for connecting the wire which forms the loops to a suitable source of direct current capable of supplying relatively high current for short periods of time.
  • the supporting rotor framepiece element 27 of the rotor 21 be comprised of non-magnetic material such as plastic rather than of a magnetically conductive material such as iron.
  • FIG. 3 which shows the motor embodiment of FIG. 1 in assembled form
  • the stator flux generated by the field coil 18 follows a circuit path of extremely low reluctance.
  • the air gaps through which the magnetic flux passes between the rotary and stationary elements of the motor are of extremely small and narrow dimension.
  • stator magnetic flux that is, starting from the base of the stator piece 14 as a point of departure, the flux travels in a path radially outward, then parallel to the axis of the motor and upward along the stator pole members 13, next transversely of the axis across the air gap to the rotor poles 31 on the peripheral ring member 30 of the rotor 21, continuing through the respective thicknesses of the rotor ring and the lip portion 28 of the supporting framepiece 27 across another air gap to the flange portion 22a of the cup member 22, thence radially inward through the cup member 22 towards the center of the field coil 18, and finally parallel to the axis of the field coil and downward through the ferrous core piece 20 to complete the circuit path).
  • the rotor member 21, being located outside of the field coil 18, has a radius, and hence a moment arm, which is just slightly less than the overall dimension of the motor transverse to its axis of rotation.
  • the location of the air gap, in which the rotor 21 interacts with the magnetic field of the stator, outside the field coil 18 rather than inside permits, per se, the rotor to generate a torque on the order of two or more times higher by reason of the increased length available in its moment arm.
  • the motor embodiments of the present invention also possess substantial advantages over prior art devices in performance, as well as cost, because of the novel design provided for the rotor element 21.
  • the combination of a thin peripheral ring 30 of magnetized material in conjunction with a lightweight supporting framepiece 27 of non-critical material yields a rotary member possessed of a high energy product-to-mass ratio, and thus the resultant motor has exceptionally good starting and running torque for its size and weight.
  • FIGS. 2 and 4 show an alternative embodiment of the present invention which possesses substantially the same characteristics as the motor embodiment shown in FIGS. 1 and 3.
  • elements of the motor which are identical to those shown in the motor embodiment of FIGS. 1 and 3 are identified with the same reference characters; while those elements which differ only in dimension from similar elements shown in the previously-described embodiment are distinguished by prime superscripts, and elements which are substantially different are identified with new reference characters.
  • the major difference betwen the two embodiments is that, in the latter, the stator pole piece and the ferromagnetic cup member have changed places in the motor.
  • the principal elements of this embodiment of the motor' comprise the mounting plate 12, a ferromagnetic cup member 15 having a peripheral flange portion 15a, the field coil 18, a stator polar structure 23 having a plurality of salient pole members 24 projecting from its periphery, and a permanent magnet rotor 21'.
  • the flange portion 15a of the cup member 15 which overlaps the pole members 24 of the stator piece 23 rather than the other way around.
  • the magnetized peripheral ring member 30' is attached around the inside of the lip portion 28 of the circular supporting framepiece 27 rather than around the outside.
  • the construction and operation of this motor embodiment are substantially identical to that of the previously-described embodiment.
  • Both of these motor embodiments posses-s the reliable self-starting characteristic common to motors of the type described in the Everard et al. patent.
  • the construction of the stator, rotor, and the other magnetic circuit elements, their physical configuration, their magnetic properties (reluctance), and their mutual interrelationships aid in causing the rotor consistently to assume the preferred quiescent position described in the aforesaid patent, and to start reliably when the stator poles are energized.
  • the motor of the present invention will start and run either in a clockwise direction or in a counterclockwise direction, depending upon the exact moment when it is energized and hence upon the phase or polarity condition of the energizing current when the motor is energized.
  • This bi-directional characteristic is satisfactory for a number of motor applications.
  • any of several common mechanical no-back devices may be incorporated, or alternatively, various non-mechanical arrangements may be employed to assure unidirectional operation.
  • a stator piece having a set of salient stator poles, 'a field coil magneticallycoupled to said stator piece for producing an alternating magnetized flux field in the salient stator poles of said motor, said salient stator poles extending from an end of said coil longitudinally along the length of and outside the same, a magnetic circuit member of low reluctance connected to said field coil and having a portion outside of the coil juxtaposed near the ends of the poles of said stator piece with an air gap inbetween, said magnetic member having a substantially smoothly contoured portion in the region facing said salient stator poles, said coil being magnetically coupled to said stator piece and to said magnetic circuit member, whereby at any instant all of said stator poles are of one magnetic polarity and said smoothly contoured portion of said magnetic circuit member has the opposite magnetic polarity, and a permanent-magnet rotor having a plurality of poles of alternate polarity spaced around its periphery and mounted for rotation in the magnetic field
  • An A.C. synchronous motor having high efficiency and high torque characteristics comprising: a field coil for producing alternating magnetic flux; stator means of low reluctance magnetic material in magnetic circuit relation with said coil for guiding said flux; said stator means including a portion forming a magnetic path extending radially near an end of said coil and then longitudinally along said coil outside the same to form a smoothly contoured, or non-salient, periphery, and a plurality of salient pole members of the same instantaneous magnetic polarity extending from the other end of said coil longitudinally along said coil outside the same; the periphery of said stator portion and .the ends of said salient pole members overlapping so as to leave an air gap inbetween; and a permanent-magnetic rotor having a plurality of poles of alternate polarity spaced around its periphery and mounted for rotation in the magnetic field provided in said air gap by said field coil and said stator means; said stator means and said rotor forming thereby a closed path
  • An A.C. synchronous motor having 'high efliciency and high torque characteristics comprising: a field coil wound in a cylindrical form around an axis for producing alternating magnetic flux; circularly symmetrical stator means of low reluctance magnetic material mounted concentrically with said coil and in magnetic circuit relation therewith for guiding said flux, said stator means including :a cup-like portion forming a magnetic path extending radially outward near an end of said coil and then longit-udinally along said coil outside the same to a smoothly contoured, or non-salient, edge region, and a plurality of spaced finger-like pole members of the same instantaneous magnetic polarity extending from the other end of said coil longitudinally along said coil outside the same; the edge region of said cup-like portion and the ends of said pole members overlapping so as to leave inbetween a narrow annular air gap concentric with said coil; and a permanent-magnetic disc-shaped rotor of larger diameter than said field coil having a plurality of pole
  • a stator piece having a single set of substantially equally-spaced salient stator poles, a field coil magnetically-coupled to said stator piece for producing an alternating magnetized flux field of the same phase relationship in all the salient stator poles of said motor, said salient stator poles extending from an end of said coil longitudinally along the length of and outside the same, a cup-like ferromagnetic member attached to said field coil and having a flange element having an instantaneously oppositely magnetic polarity from the polarity extending from the other end of said coil longitudinally along the length of and outside the same, said flange having a smoothly contoured region not divided into salient poles, said region and the ends of the poles of said sta-tor piece overlapping with an annular air gap inbetween, and a permanent-magnet rotor having a plurality of poles of alternate polarity spaced around its periphery and mounted for rotationin the magnetic field provided in said annular air
  • a motor according to claim 5 in which said permanent-magnet rotor comprises a circular supporting element and a thin annular ring of magnetized anisotropic ferrite material in a suitable binder afiixed to the periphery of said element.
  • the rotor of claim 5 characterized in that the magnetizable anisotropic ferrite material in a suitable binder is rubber-bonded barium ferrite material.
  • An A.C. synchronous motor having high efiiciency and high torque characteristics comprising: a cylindrical field coil having two ends; a stator structure comprising a first low-reluctance portion at one end of said field 8 coil and magnetically coupled therewith and extending radially outwardly to a peripheral edge, and a second low-reluctance magnetic portion at the other end of said field coil magnetically linked therewith and extending radially outward and axially along the outside of said coil toward said first portion and terminating in an edge lying in a cylinder adjacent to the peripheral edge of said first portion, one of said edges having salient poles formed therein to concentrate magnetic flux and the other of said edges having a smooth, or non-salient, contour radially spaced from said salient poles, said first and second portions of said stator structure being oppositely magnetically polarized when said coil is energized; and a rotor comprising a ring of permanent magnetic material between, and radially spaced from, both of said edges, said ring

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Permanent Field Magnets Of Synchronous Machinery (AREA)
  • Synchronous Machinery (AREA)
US259880A 1963-02-20 1963-02-20 Synchronous motors Expired - Lifetime US3253169A (en)

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Application Number Priority Date Filing Date Title
US259880A US3253169A (en) 1963-02-20 1963-02-20 Synchronous motors
NL6401518A NL6401518A (sk) 1963-02-20 1964-02-19
BE644065D BE644065A (sk) 1963-02-20 1964-02-19
DE19641488127 DE1488127A1 (de) 1963-02-20 1964-02-20 Wechselstromsynchronmotor

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US259880A US3253169A (en) 1963-02-20 1963-02-20 Synchronous motors

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Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3355645A (en) * 1963-07-18 1967-11-28 Maeda Hisao Constant speed electric motors including a vibrating magnetic drive
US3495107A (en) * 1969-04-28 1970-02-10 Tri Tech Cylindrical stepper motor having a stator biasing magnet
US3555325A (en) * 1968-01-31 1971-01-12 Tokai Rika Co Ltd Miniature electric synchronous motor
US3659128A (en) * 1969-11-17 1972-04-25 Autotrol Corp Icemaker drive with overload release
US3746900A (en) * 1972-03-01 1973-07-17 Amf Inc Synchronous motor with improved starting characteristics
US3755701A (en) * 1972-09-14 1973-08-28 Gen Motors Corp Selectively reversible step motor
FR2404274A1 (fr) * 1977-09-22 1979-04-20 Sony Corp Lecteur de disque
US4329606A (en) * 1979-12-10 1982-05-11 General Scanning, Inc. Electric motor construction
EP0296691A1 (en) * 1987-06-26 1988-12-28 Kinetron B.V. Electro-mechanical timepiece with stepper motor
US4841186A (en) * 1987-03-31 1989-06-20 Standard Elektrik Lorenz Aktiengesellschaft Electronically commutated, collectorless directed-current motor
US5406158A (en) * 1993-07-23 1995-04-11 Eaton Corporation Miniature synchronous motor
US6157107A (en) * 1998-04-10 2000-12-05 Canon Kabushiki Kaisha Motor with magnetic stator poles inside and outside the rotor magnet

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102016011156A1 (de) * 2016-09-16 2018-03-22 Minebea Co., Ltd. Verfahren und Vorrichtung zum Magnetisieren von Rotormagneten zur Verwendung in elektrischen Maschinen

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2572632A (en) * 1948-01-26 1951-10-23 Sangamo Electric Co Synchronous motor
US2999275A (en) * 1958-07-15 1961-09-12 Leyman Corp Mechanical orientation of magnetically anisotropic particles
US3059131A (en) * 1961-05-10 1962-10-16 Cons Electronies Ind Corp Synchronous motors
US3122666A (en) * 1959-03-27 1964-02-25 Berex Establishment Universal synchronous motor

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2572632A (en) * 1948-01-26 1951-10-23 Sangamo Electric Co Synchronous motor
US2999275A (en) * 1958-07-15 1961-09-12 Leyman Corp Mechanical orientation of magnetically anisotropic particles
US3122666A (en) * 1959-03-27 1964-02-25 Berex Establishment Universal synchronous motor
US3059131A (en) * 1961-05-10 1962-10-16 Cons Electronies Ind Corp Synchronous motors

Cited By (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3355645A (en) * 1963-07-18 1967-11-28 Maeda Hisao Constant speed electric motors including a vibrating magnetic drive
US3555325A (en) * 1968-01-31 1971-01-12 Tokai Rika Co Ltd Miniature electric synchronous motor
US3495107A (en) * 1969-04-28 1970-02-10 Tri Tech Cylindrical stepper motor having a stator biasing magnet
US3659128A (en) * 1969-11-17 1972-04-25 Autotrol Corp Icemaker drive with overload release
US3746900A (en) * 1972-03-01 1973-07-17 Amf Inc Synchronous motor with improved starting characteristics
US3755701A (en) * 1972-09-14 1973-08-28 Gen Motors Corp Selectively reversible step motor
FR2404274A1 (fr) * 1977-09-22 1979-04-20 Sony Corp Lecteur de disque
US4329606A (en) * 1979-12-10 1982-05-11 General Scanning, Inc. Electric motor construction
US4841186A (en) * 1987-03-31 1989-06-20 Standard Elektrik Lorenz Aktiengesellschaft Electronically commutated, collectorless directed-current motor
AU604102B2 (en) * 1987-03-31 1990-12-06 Standard Elektrik Lorenz Aktiengesellschaft A direct current motor
EP0296691A1 (en) * 1987-06-26 1988-12-28 Kinetron B.V. Electro-mechanical timepiece with stepper motor
US4908808A (en) * 1987-06-26 1990-03-13 Kinetron B.V. Timepiece having a multipolar rotor
US5406158A (en) * 1993-07-23 1995-04-11 Eaton Corporation Miniature synchronous motor
US6157107A (en) * 1998-04-10 2000-12-05 Canon Kabushiki Kaisha Motor with magnetic stator poles inside and outside the rotor magnet

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BE644065A (sk) 1964-08-19
DE1488127A1 (de) 1969-08-28
NL6401518A (sk) 1964-08-25

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